"Philippe Huber" ha scritto
>I have a dummy question: I would like to know if it is possible (and how)
to
>differentiate a symbolic sum like
>
>f(x1,...,xn)=Sum[x^2[[k]],{k,1,p}]
>
>with respect to xi. I should obtain 2xi.
If you mean a term by term differentiation, you could try the Summa package
I uploaded on the mathsource a couple of years ago. It's a very thin and
almost trivial package but it can avoid you typing substitutions rules at
each passage.
http://www.mathsource.com/Content/Enhancements/MathFunctions/0210-508
hope this can be of some help,
regards,
Peltio
peltio at despammed dot com
PS
The address inside the package is no longer valid.